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Synlett 2006(13): 2067-2070  
DOI: 10.1055/s-2006-949610
LETTER
© Georg Thieme Verlag Stuttgart · New York

New Cyclic Arg-Gly-Asp Pseudopentapeptide Containing the β-Turn Mimetic GPTM

Maria Salvatia, Franca M. Cordero*a, Federica Pisaneschia, Nicoletta Cinib, Anna Bottoncettib, Alberto Brandi*a
a Department of Organic Chemistry ‘Ugo Schiff’, Laboratory of Design, Synthesis and Study of Biologically Active Heterocycles, University of Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino (FI), Italy
Fax: +39(055)4573531; e-Mail: franca.cordero@unifi.it; e-Mail: alberto.brandi@unifi.it;
b Department of Clinical Physiopathology, Nuclear Medicine Unit, University of Firenze, viale G. Pieraccini 6, 50134 Firenze, Italy
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Publication History

Received 31 May 2006
Publication Date:
09 August 2006 (online)

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Abstract

The solid-phase synthesis of cyclic pseudopeptides containing the Arg-Gly-Asp recognition sequence and the dipeptide isostere 2-amino-3-oxotetrahydro-1H-pyrrolizine-7a(5H)-carboxylic acid (GPTM) was accomplished. N-Fmoc-Asp-OAll was anchored to Wang resin through its side chain and sequentially coupled with N-Fmoc-Gly-OH, N-Fmoc-Arg(Pbf)-OH and N-Fmoc-GPTM-OH. The supported linear pentapeptide smoothly underwent head-to-tail cyclization by activation with TBTU/DIPEA. Finally, TFA treatment released the completely deprotected cyclic pseudopentapeptide. Competition binding assays to purified α V β3 and α V β5 integrins showed a high inhibitory activity of cyclo[Arg-Gly-Asp-(2S,7aS)-GPTM].

Key words

cyclic peptides - solid-phase synthesis - heterocycles - integrin antagonists - dipeptide isosteres

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Analytical Data for Cyclo[Arg-Gly-Asp-(2S,7aS)-GPTM] (3). Yield of 14% with respect to N-Fmoc-Asp(Wang-resin)-OAll loading; [α]D 20 +44.0 (c 0.3, H2O). 1H NMR (400 MHz, D2O): δ = 4.10 (t, J = 7.7 Hz, 1 H, H-Cα Arg), 4.05 (d, J = 14.2 Hz, 1 H, H-Cα Gly), 3.42 (d, J = 14.1 Hz, 1 H, H-Cα Gly), 3.34 (dt, J = 11.7, 8.2 Hz, 1 H, 5-Ha GPTM), 3.16-3.02 (m, 3 H, 5-Hb GPTM, H-Cδ Arg), 2.78 (dd, J = 7.6, 6.0 Hz, 2 H, H-Cβ Asp), 2.47 (dd, J = 14.3, 8.2 Hz, 1 H, 1-Ha GPTM), 2.29 (dd, J = 12.3, 5.7 Hz, 1 H, 7-Ha GPTM), 2.13 (d, J = 14.3 Hz, 1 H, 1-Hb GPTM), 2.12-2.08 (m, 1 H, 6-Ha GPTM), 1.84-1.77 (m, 1 H, 7-Hb GPTM), 1.70 (q, J = 7.7 Hz, 2 H, H-Cβ Arg), 1.62-1.43 (m, 3 H, 6-Hb GPTM, H-Cγ Arg). 1H NMR (400 MHz, DMSO-d 6): δ = 12.20 (br s, 1 H, CO2H), 8.66 (br t, J = 6.1 Hz, 1 H, NH Gly), 8.41 (d, J = 6.8 Hz, 1 H, NH Arg), 8.28 (d, J = 9.0 Hz, 1 H, NH GPTM), 7.44 (br s, 2 H, NH2 Arg), 7.40-7.38 (m, 1 H, C=NH Arg), 7.13 (d, J = 9.2 Hz, 1 H, NH Asp), 4.56 (dt, J = 8.4, 5.1 Hz, 1 H, 2-H GPTM), 4.47 (dt, J = 8.5, 4.3 Hz, 1 H, H-Cα Asp), 4.07 (q, J = 7.2 Hz, 1 H, H-Cα Arg), 4.00 (dd, J = 13.9, 7.8 Hz, 1 H, H-Cα Gly), 3.48-3.45 (m, 1 H, 5-Ha GPTM), 3.19 (dd, J = 13.9, 4.4 Hz, 1 H, H-Cα Gly), 3.12-3.07 (m, 2 H, H-Cδ Arg), 2.99-2.92 (m, 1 H, 5-Hb GPTM), 2.69 (dd, J = 16.7, 8.4 Hz, 1 H, 1-Ha GPTM), 2.41 (dd, J = 16.7, 4.8 Hz, 1 H, 1-Hb GPTM), 2.34-2.29 (m, 3 H, 7-Ha GPTM, H-Cβ Asp), 2.09 (d, J = 14.0 Hz, 1 H, 7-Hb GPTM), 1.85-1.77 (m, 1 H, 6-Ha GPTM), 1.73-1.42 (m, 5 H, 6-Hb GPTM, H-Cβ Arg, H-Cγ Arg). 13C NMR (100 MHz, D2O): δ = 179.8, 177.41, 177.36, 174.4, 173.7, 173.5 (s, CO), 159.3 (s, CN), 77.3 (s, C-7a GPTM), 58.9 (d, C-2 GPTM), 57.7 (d, Cα Arg), 51.6 (d, Cα Asp), 46.5 (t, Cα Gly), 43.5 (t, C-5 GPTM), 43.0 (t, Cδ Arg), 41.7 (t, C-1 GPTM), 37.1 (t, Cβ Asp), 36.8 (t, C-7 GPTM), 28.7 (t, Cβ Arg), 28.5 (t, Cγ Arg), 27.0 (t, C-6 GPTM). MS (ESI): 495 [MH+].

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The reproducibility of the IC50 values was proved by performing the same tests on the antagonist cyclo(-Temp8-Arg-Gly-Asp-) reported by Belvisi et al. in ref. 6e.